1 Field of the Invention
This invention relates to an information recording and reproducing apparatus which may faithfully take out original informations in utilizing a recording and reproducing system wherein informations are lacking in a particular frequency.
2. Description of Prior Arts
The art of "perpendicular magnetic recording" is detailed in, for example, IEEE TRANSACTIONS ON MAGNETICS, Vol. MAG-16, No. 5 containing a thesis entitled: "Studies of the Perpendicular Magnetization Mode in Co-Cr Sputtered Films". FIG. 1 of the accompanying drawing illustrates one example of an arrangement for such perpendicular magnetic recording. That is, a principal magnetic pole 1 made of a thin film of permalloy having high magnetic permeability is provided, in confrontation to which an auxiliary magnetic pole 2 with a winding 3 being wound therearound is positioned at a predetermined distance from the principal magnetic pole 1, and a magnetic recording medium 4 is interposed between these two magnetic poles. The recording medium 4 is made up of a perpendicular recording layer 5 of Co-Cr alloy and a highly permeable layer 6, both layers 5 and 6 being formed on a base (or substrate) 7.
With the above-described construction of the perpendicular magnetic recording system, when current conduction is effected through the winding 3 on the auxiliary magnetic pole 2, there is generated a magnetic line of force which flows from the auxiliary magnetic pole 2 through the highly permeable layer 6 and converges on the principal magnetic pole 1. At this instant, the perpendicular magnetic recording is effected to the recording layer 5 adjacent to the highly permeable layer 6. The system is also constructed in such a way that, at the time of reproduction, the magnetic line of force from the magnetic recording medium 4 induces flux changes in the winding 3 by its interaction with the principal magnetic pole 1 to thereby obtain a reproduction output.
It has already been known that the frequency characteristic of this perpendicular magnetic recording system at the time of reproduction is in a comb-teeth form, as shown in FIG. 2, as determined by the thickness t of the principal magnetic pole 1, wherein a frequency band incapable of producing outputs exists at several points. Also, a low frequency region is generally shut off in the magnetic recording system. When a signal having a broad spectral distribution as shown in FIG. 3 is put in the recording and reproducing system having such frequency characteristic as mentioned above, there appear in the spectrum those portions lacking information which makes it difficult to faithfully record or reproduce the original signal. On account of this, there has so far been used a peak portion of a frequency band in the lowest frequency, hence it has been difficult to use even those high frequency portions such as the second and third peaks.